Final answer:
Disinfection is the first step in wastewater treatment as it kills pathogens and harmful bacteria in the wastewater.
Step-by-step explanation:
Disinfection is an important step in wastewater treatment as it kills pathogens and harmful bacteria in the processed wastewater. Chlorine and other chemicals are added to a disinfection tank to achieve this. However, it is important to be cautious as excessive quantities of chlorine can be harmful.